Why is there a type conversion error in this code?

Question

I don't understand why the line this.claim = claim; has the error "Cannot convert type 'A' to type 'Claim'". I need to return an observable because this function is called in a resolver. I don't actually need to return the claim itself, I just need to set the property on ClaimStoreService, but I couldn't figure out how to return an empty or void observable.

export class ClaimStoreService {

    constructor(private readonly claimService: ClaimService) { }

    claim: Claim;

    getClaim(guid: string): Observable<Claim> {
        return this.claimService.get(guid).pipe(
            take(1),
            mergeMap(claim => {
                // Cannot convert type 'A' to type 'Claim'
                this.claim = claim;
                return of(claim);
            }));
    }
}

I hate errors like that and I also hate using any. However, have you tried using mergeMap((claim: any) => or mergeMap((claim:Claim) => or return this.claimService.get<Claim>(guid) ? — Thomas Cayne
– Thomas Cayne, Commented Nov 6, 2019 at 16:00

Palak Jadav · Accepted Answer · 2019-11-06 15:59:42Z

1

claim: Claim;

getClaim(guid: string): Observable<Claim> {
        return this.claimService.get(guid).pipe(
            take(1),
            // give type here will solve your issue
            mergeMap((claim:Claim) => {
                this.claim = claim;
                return of(claim);
            }));
    }

answered Nov 6, 2019 at 15:59

Palak Jadav

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1 Comment

Jamie Ide Over a year ago

Thank you! That didn't occur to me because I wasn't getting a type error on return of(claim). I was also seeing the correct type when hovering but that may be ReSharper. I'll accept as soon as I can.

Thomas Cayne · Accepted Answer · 2019-11-06 16:14:51Z

0

I think if you use this.claimService.get<Claim>(guid) you don't have to type claim in mergeMap(claim =>.

answered Nov 6, 2019 at 16:14

Thomas Cayne

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